Tank Waste Research Articles

Small to Full-Height Scale Comparisons of Cesium Ion Exchange Performance with Crystalline Silicotitanate

ABSTRACT Crystalline silicotitanate (CST) ion exchanger is planned for use in the removal of cesium (137Cs) from the aqueous phase of Hanford tank wastes in preparation for vitrification at the Waste Treatment and Immobilization Plant (WTP). Batch contact testing was conducted to assess cesium exchange kinetics at four different CST particle-size distributions. Column testing was conducted at three column sizes, small (2.5% full height), medium (12% full height), and full height, to assess Cs loading performance behavior. Testing at the small scale was compared to actual Hanford tank waste testing to verify the validity of simulant tests to reflect full-height column performance. CST particle size adjustment was essential in scaling the column dynamics down from full scale to medium and small scales. The mean (d 50) CST particle size needed to be reduced from 633 microns to 567 and 542 microns, respectively, to achieve appropriately scaled results. Based on these results, a determination of intraparticle and film-diffusion impacts on overall mass-transfer coefficients will allow future modeling of the breakthrough performance at a range of process conditions.

The Removal of Residual Concentration of Hazardous Metals in Wastewater from a Neutralization Station Using Biosorbent-A Case Study Company Gutra, Czech Republic.

This article deals with the possibility of using a biosorbent in the form of a mixture of cones from coniferous trees to remove the residual concentration of hazardous metals contained in hazardous waste, which is disposed of in a neutralization station. The efficiency of the tested biosorbent in removing Ni, Zn, Cu, and Fe was monitored here. Laboratory research was carried out before the actual testing of the biosorbent directly in the operation of the neutralization station. With regard to the planned use of the biosorbent in the operational test, the laboratory experiments were performed in a batch mode and for the most problematic metals (Ni and Zn). The laboratory tests with real wastewater have shown that the biosorbent can be used to remove hazardous metals. Under the given conditions, 96% of Ni and 19% of Zn were removed after 20 min when using NaOH activated biosorbent with the concentration of 0.1 mol L−1. The inactivated biosorbent removed 93% of Ni and 31% of Zn. The tested biosorbent was also successful during the operational tests. The inactivated biosorbent was applied due to the financial costs. It was used for the pre-treatment of hazardous waste in a preparation tank, where a significant reduction in the concentration of hazardous metals occurred, but the values of Ni, Cu, and Zn still failed to meet the emission limits. After 72 h, we measured 10 mg L−1 from the original 4,056 mg L−1 of Ni, 1 mg L−1 from the original 2,252 mg L−1 of Cu, 1 mg L−1 from the original 4,020 mg L–1 of Zn, and 7 mg L−1 from the original 1,853 mg L−1 of Fe. However, even after neutralization, the treated water did not meet the emission limits for discharging into the sewer system. The biosorbent was, therefore, used in the filtration unit as well, which was placed in front of the Parshall flume. After passing through the filtration unit, the concentrations of all the monitored parameters were reduced to a minimum, and the values met the prescribed emission limits. The biosorbent was further used to thicken the residual sludge in the waste pre-treatment tank, which contributed to a significant reduction in the overall cost of disposing of residual hazardous waste. This waste was converted from liquid to solid-state.

Identification and Quantification of Technetium Species in Hanford Waste Tank AN-102.

Technetium-99 (Tc), a high yield fission product generated in nuclear reactors, is one of the most difficult contaminants to address at the U.S. Department of Energy Hanford, Savannah River, and other sites. In strongly alkaline solutions typifying Hanford tank waste, Tc exists as pertechnetate (TcO4-) (oxidation state VII) as well as in reduced forms (oxidation state < VII), collectively known as non-pertechnetate (non-TcO4-) species. Designing strategies for effective Tc management, including separation and immobilization, necessitates understanding the molecular structure of the non-TcO4- species and their identification in actual tank waste samples. Identification of non-TcO4- species would facilitate the development of new treatment technologies effective for dissimilar Tc species. Toward this objective, a spectroscopic library of the Tc(I) [fac-Tc(CO)3]+ and Tc(II, IV, V, VII) compounds was generated and applied to the characterization of the actual Hanford AN-102 tank waste supernatant, which was processed to adjust Na concentration to ∼5.6 M and remove 137Cs by spherical resorcinol-formaldehyde (sRF) ion-exchange resin. Post 137Cs removal, the cesium-loaded sRF column was eluted with 0.45 M HNO3. As-received AN-102, Cs-depleted effluent, and sRF eluate fractions were comprehensively characterized for chemical composition and speciation of Tc using 99Tc nuclear magnetic resonance spectroscopy and X-ray absorption spectroscopy. It was demonstrated for the first time that non-TcO4- Tc present in the AN-102 tank waste is composed of several low-valent Tc species, including the Tc(I) [fac-Tc(CO)3]+ and Tc(IV) compounds. This is the first demonstration of multiple non-TcO4- species co-existing in the Hanford tank waste, highlighting their importance for the waste processing.

Off-gas rhenium capture and recovery in a laboratory-scale melter

The path for immobilizing low-activity waste (LAW), a mixture of salts, for long-term storage is adding glass-forming and modifying additives and minerals to the solution and vitrifying the resulting slurry in an electric melter. Technetium-99 (99Tc), a long-lived radionuclide present in LAW, is highly volatile at the elevated temperatures in a glass melt. An off-gas system was designed for capturing volatile 99Tc or Re, its nonradioactive surrogate, during continuous charging of a LAW melter feed in a laboratory-scale melter (LSM). The Re retention in the glass was determined via the measured amount of volatilized Re in the off-gas during a time period when the reacting melter feed was at a quasi-steady-state. This study was performed in preparation for the LSM system to be applied for melter feeds containing either a LAW simulant spiked with 99Tc or an actual tank waste.

Elemental characterization of crystalline silicotitanate following Hanford tank waste processing

ABSTRACT To expedite vitrification of low activity waste at the Hanford Site, a Tank-Side Cesium Removal system, using crystalline silicotitanate (CST) as the ion exchange media, is being evaluated. Laboratory scale testing of Cs removal by CST from Hanford tank waste supernates has been conducted by Pacific Northwest National Laboratory. Selectivity and partitioning of analytes on spent CST, specifically RCRA hazardous metals, selected +2 cations, and transuranic elements, were characterized through the complete digestion of CST. The CST was shown to adsorb a relevant fraction of Ca, Cd, Pb, Sr, U, Pu, Np, Am, and potentially Fe by IX and/or other mechanisms.

RETRACTED ARTICLE: Direct quantification of iodine in nuclear wastes using DRC-ICP-MS

A method was developed for the direct quantification of iodine in Hanford tank waste using inductively coupled plasma mass spectrometry coupled with a dynamic reaction cell. The following parameters were optimized to lower the 129 m/z background signal and minimize iodine carryover effects: diluent, oxygen gas flow rate, radiofrequency voltage applied to the dynamic reaction cell, and rinse times. The concentration of 129I was 23 ± 1 µg/mL (n = 4, ± 1σ) in the Hanford waste tank 241-AP-107; to our knowledge this work constitutes the first report of iodine concentration in the tank waste.

Моделирование рабочих процессов саморегенерирующихся фильтров, функционирующих в смазочных системах судовых дизелей

The article highlights the urgency of the research of working processes of a self-cleaning filter designed to purify the engine oil in the internal combustion engines. There was carried out experimental modeling of countercurrent regeneration of self-cleaning filters used in fuel preparation and diesel lubrication systems on ships. The layout of the unit for modeling the working processes of self-regenerating filters includes a service tank, a hydraulic motor with a stirrer, a pump, a hydraulic cylinder, a receiver of compressed air, a waste tank, a filtering element, shut-off and pneumatic control equipment, a pollution gauge, a temperature sensor, and other elements. A planning matrix is formed, and the experiment results on evaluating the efficiency of the self-regenerating filters are illustrated. The main factors of the regeneration coefficient are considered. There are presented the dependencies of evaluating the process effectiveness and predicting the life of filters between dry cleanings. The methods of calculating the regeneration parameters of automated filters based on the SRF-60 and SRFD-120 modules have been presented, which allows choosing the hydrodynamic modes and backwash time of filter elements taking into account the operating conditions of oil filters. The influence of the filtering process regeneration efficiency identified by the specific intensity of the removal of the dispersed phase from the oil, hydrodynamics (Reynolds number) and the relative backwash time, the adhesive properties of sludge, the filter design, and dispersion of the pollution are analyzed. The evidence of the validation of the calculated experimental dependences obtained from the laboratory tests of the filter model and their compliance with the results of field tests of self-cleaning filters on ships are presented. The possibility of calculating and adjusting the off-line operation of the self-cleaning filter in the lubrication systems of marine diesel engines is presented subject to diesel forcing, fuel quality and lubricants used, oil aging, additives wear and contamination by coarse-grained mechanical impurities.

Effect of Cr(III) Adsorption on the Dissolution of Boehmite Nanoparticles in Caustic Solution.

The incorporation of relatively minor impurity metals onto metal (oxy)hydroxides can strongly impact solubility. In complex highly alkaline multicomponent radioactive tank wastes such as those at the Hanford Nuclear Reservation, tests indicate that the surface area-normalized dissolution rate of boehmite (γ-AlOOH) nanomaterials is at least an order of magnitude lower than that predicted for the pure phase. Here, we examine the dissolution kinetics of boehmite coated by adsorbed Cr(III), which adheres at saturation coverages as sparse chemisorbed monolayer clusters. Using 40 nm boehmite nanoplates as a model system, temperature-dependent dissolution rates of pure versus Cr(III)-adsorbed boehmite showed that the initial rate for the latter is consistently several times lower, with an apparent activation energy 16 kJ·mol-1 higher. Although the surface coverage is only around 50%, solution analysis coupled to multimethod solids characterization reveal a phyicochemical armoring effect by adsorbed Cr(III) that substantially reduces the number of dissolution-active sites on particle surfaces. Such findings could help improve kinetics models of boehmite and/or metal ion adsorbed boehmite nanomaterials, ultimately providing a stronger foundation for the development of more robust complex radioactive liquid waste processing strategies.

Effect of cold cap coverage and emissivity on the plenum temperature in a pilot‐scale waste vitrification melter

AbstractIntegrated computational fluid dynamics (CFD) models are being developed to model the complex physics occurring within the high‐level waste melter for vitrification of legacy tank waste at the Hanford site. This study presents a validation of the integrated CFD model by using data from two experimental runs in a pilot‐scale melter. While the model uses several simplifying assumptions (such as constant heat sinks from a cooling jacket and inleakage of ambient air, steady state feed‐to‐batch conversion heat, and a cold cap model with a simplified shape), it closely predicts the molten glass (1150°C and 1175°C) and plenum temperatures (550°C) obtained from thermocouples during two pilot‐scale tests, with an average cold cap coverage of 80%. Additional simulations were performed to explore the sensitivity of the predicted plenum temperatures to variations in cold cap coverage (fraction of melt surface covered by the glass batch) and batch emissivity. The plenum temperature was found to be in the range of 606°C when cold cap coverage decreased from 95% to 70%. Cold cap emissivity had a smaller effect, increasing the plenum temperature by as much as 179°C when cold cap emissivity increased from 0.2 to 0.8. Maintaining a high cold cap coverage without overfeeding is important for a sustained melter operation with high glass throughput. This work provides a tool for achieving that goal in terms of correlating the plenum temperature with the cold cap coverage.

Evaluation of technological wastewater treatment solutions for the settlements within the Backo Podunavlje biosphere reserve

This paper presents the results of a multidisciplinary analysis and the evaluation of a suitable technological solution for wastewater treatment for the villages Backi Breg and Kolut, belonging to the Backo Podunavlje Biosphere Reserve. The research was structured as a three part methodology. It encompassed: 1) citizens? habits on wastewater production - investigated by analysing septic tank waste water quality; 2) stakeholders? opinion on the most important features which a wastewater treatment facility (WWTF) has to fulfil-analysed by interviewing stakeholders and the application of multi-criteria decision support tool and 3) finding the most suitable location for future WWTF by applying geographic information systems (GIS). The results revealed that sampled wastewaters were in range for municipal wastewaters. The decision-making model, based on simple additive weighting (SAW), was defined to evaluate two possible solutions (constructed wetland and sequencing batch reactor) across six criteria. The model showed that a constructed wetland system is more adequate, in comparison to the sequencing batch reactor. Finally, by overlapping multiple GIS map layers the most suitable area for setting up the WWTF was found. The proposed methodology is especially suitable for application in biosphere reserves, since the link social attitude - natural resources exploitation - nature conservation is the key element for achieving sustainability.

On the Active Adsorption of Chromium(III) from Alkaline Solutions Using Multiwalled Carbon Nanotubes

The present investigation deals with the adsorption of chromium(III) from alkaline media, as representative of highly-caustic component solutions of nuclear tank wastes, using multiwalled carbon nanotubes. The adsorption of Cr(III) has been studied under various experimental conditions, i.e., stirring speed of the aqueous solution, initial metal and adsorbent concentrations, NaOH concentration in the aqueous solution, and temperature. The rate law indicated that chromium adsorption is well represented by the particle diffusion model, whereas the adsorption process fits with the pseudo-second order kinetic model within an exothermic setting. Equilibrium data fit to the Langmuir type-2 equilibrium isotherm in a spontaneous process. Chromium(III) can be eluted from metal-loaded nanotubes using acidic solutions, from which fine chromium(III) oxide pigment can ultimately be yielded.

The Interdependence of Autonomous Human-Machine Teams: The Entropy of Teams, But Not Individuals, Advances Science

Key concepts: We review interdependence theory measured by entropic forces, findings in support, and several examples from the field to advance a science of autonomous human-machine teams (A-HMTs) with artificial intelligence (AI). While theory is needed for the advent of autonomous HMTs, social theory is predicated on methodological individualism, a statistical and qualitative science that neither generalizes to human teams nor HMTs. Maximum interdependence in human teams is associated with the performance of the best teams when compared to independent individuals; our research confirmed that the top global oil firms maximize interdependence by minimizing redundant workers, replicated for the top militaries in the world, adding that impaired interdependence is associated with proportionately less freedom, increased corruption, and poorer team performance. We advanced theory by confirming that the maximum interdependence in teams requires intelligence to overcome obstacles to maximum entropy production (MEP; e.g., navigating obstacles while abiding by military rules of engagement requires intelligence). Approach: With a case study, we model as harmonic the long-term oscillations driven by two federal agencies in conflict over closing two high-level radioactive waste tanks, ending when citizens recommended closing the tanks. Results: While contradicting rational consensus theory, our quasi-Nash equilibrium model generates the information for neutrals to decide; it suggests that HMTs should adopt how harmonic oscillations in free societies regulate human autonomy to improve decisions and social welfare.

Evaluation of four commercial tests for detecting ceftiofur in waste milk bulk tank samples.

The objective of this study was to identify factors affecting the accuracy of four commercial tests for ceftiofur drug residue in milk samples from bulk tank waste milk (WM). WM samples were collected from 12 California dairy farms which were initially tested using liquid chromatography (LC-MS/MS) to confirm their negative status for drug residues above the FDA established tolerance/safe levels. The milk samples were also tested for fat, protein, lactose, solids non-fat (SNF), somatic cell count (SCC), coliform count, and standard plate count (SPC). Each WM sample was divided into two aliquots, one labeled as negative for drug residues (WMN) and the second spiked with ceftiofur as positive for ceftiofur residues (WMPos). Both types of WM samples were tested to evaluate the performance of 4 commercially available tests: Penzyme® Milk Test, SNAP® β-lactam, BetaStar® Plus and Delvo SP-NT®. Three assays in triplicates for the WMN and WMPos were conducted for each WM sample. Test were evaluated using sensitivity, specificity, positive predictive value, negative predictive value and positive likelihood ratio. Kruskal-Wallis method was used to evaluate the effect of milk quality parameters on true positive (TP) and false negative (FN) test results. All WMPos samples were identified as positive by all four tests, rendering 100% sensitivity for each test. The specificity for Penzyme, BetaStar, Delvo, and SNAP tests were 59.2, 55.5, 44.4, and 29.6, respectively. Overall, all tests correctly identified samples with ceftiofur residues (WMPos), as shown by 100% sensitivity. Greater variability was observed regarding identification of samples free of any drug residue, with Penzyme and BetaStar having the highest risk for correctly identifying TN samples. Our findings indicate that when selecting commercial tests to detect drug residues in WM, milk quality parameters must be considered if the aim is to reduce FP test results.

Effect of Agitation to Hydrocarbon Degradation by a Hydrocarbonoclastic Bacterium isolated from Chevron Pacific Indonesia’s Waste Tank in Petapahan, Riau

Oxygen content is a limiting factor in the process of hydrocarbon compounds degradation by hydrocarbonoclastic bacteria. Oxygen may be supplied through agitation (stirring) during fermentation process by hydrocarbonoclastic bacteria. This study aims to to determine the optimal agitation speed for batch fermentation process by hydrocarbonoclastic bacteria isolated from the waste tank of PT Chevron Pacific Indonesia (CPI) Petapahan, Riau. This study was conducted in Biota laboratory, Universitas Andalas, West Sumatra, Indonesia. Hydrocarbonoclastic bacteria were recovered from waste samples by culturing into nutrient broth. Three different agitation speed viz. 110, 120, and 130 rpm were selected as optimization factors. The results show that the percentage of total petroleum hydrocarbon (TPH) degradation are 79.72, 87.49, and 88.35 for 110, 120, and 130 rpm, respectively. Meanwhile, chemical oxygen demand (COD) monitored during fermentation are 88.48, 90.06, and 90.16%, respectively. The agitation speed of 130 rpm is then designated as optimum factor for hydrocarbon degradation by hydrocarbonoclastic bacteria.

Online, Real-Time Analysis of Highly Complex Processing Streams: Quantification of Analytes in Hanford Tank Sample

Processing of hazardous materials is a crucial example where online monitoring can significantly reduce operation risk, cost, and time. This is particularly true in the case of the Hanford site, where nuclear materials from the Cold War era are being processed for environmental cleanup efforts. In exceedingly complex streams such as those at Hanford, online and real-time monitoring can be challenging due to the complexity of instrument signals. Further obstacles are imposed by the caustic nature of processing streams, as well as the radiation damage inflicted on instruments and probes. Online monitoring based on Raman spectroscopy enables the detection of many Hanford tank species of interest. Nine chemical species that comprise the majority of tank waste by volume, including Al(OH)4–, C2O42–, CO32–, CrO42–, NO3–, NO3–, OH–, PO43–, and SO42–, were detected and quantified. Real-time analysis of Raman signal allows for immediate quantification of target analytes and was successfully accomplished through the...

Large cemented gibbsite agglomerates in alkaline nuclear waste at the Hanford site and the impacts to remediation

Recent work with the remediation of legacy alkaline nuclear waste has focused on nanometer and micrometer particle sizes, emphasizing how these small particles can impact efforts to treat the waste. Building upon this work, we present here findings that show very large particles (several centimeters in size) also exist in these waste which likewise play an important role in the remediation process. While large cemented gibbsite nodules have been periodically reported in acid soils in the literature, this study found similar large gibbsite agglomerates (7 cm in diameter) in alkaline nuclear waste, the first time that such large agglomerates have been identified in an alkaline environment. The morphology of the gibbsite in the agglomerates that were grown over more than 40 years of storage in the waste tank were similar to the much smaller agglomerates that have been reported in previous shorter term studies. Fluid dynamics calculations indicate that these cemented particles would be difficult to mobilize with standard jet slurry technologies, which is consistent with their persistence in the waste heel after jet sluicing of the tank.

Improving in situ liquid SEM imaging of particles

This work presents in situ imaging of synthesized boehmite (γ‐AlOOH) particles ranging from 20 to 100 nm, suspended in liquid, in a vacuum compatible microfluidic sample holder using a scanning electron microscopy (SEM) under the high vacuum mode and highlights the advantage of in situ liquid imaging of colloids. Nanometer‐sized boehmite particles in high‐level radioactive wastes at the Hanford site are known to be difficult to dissolve and cause rheological problems for processing in the nuclear waste treatment plant. Therefore, it is important to characterize boehmite particles and understand how they form aggregates in the liquid state. Several technical advancements are made to optimize in situ liquid SEM chemical imaging resulting in the improved ability to obtain secondary electron (SE), backscattered electron (BSE) images, and energy dispersive X‐ray spectroscopy (EDX) spectra. Moreover, our results show mixed particles could be studied and identified based on the particle shape and elemental composition using in situ SEM imaging and EDX. Thus, we provide a new and improved approach to observe the evolution of particle dispersion and stability in liquid under conditions similar to those in the waste tank.

Cr(III) Adsorption by Cluster Formation on Boehmite Nanoplates in Highly Alkaline Solution.

The development of advanced functional nanomaterials for selective adsorption in complex chemical environments requires partner studies of binding mechanisms. Motivated by observations of selective Cr(III) adsorption on boehmite nanoplates (γ-AlOOH) in highly caustic multicomponent solutions of nuclear tank waste, here we unravel the adsorption mechanism in molecular detail. We examined Cr(III) adsorption to synthetic boehmite nanoplates in sodium hydroxide solutions up to 3 M, using a combination of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning/transmission electron microscopy (S/TEM), electron energy loss spectroscopy (EELS), high-resolution atomic force microscopy (HR-AFM), time-of-fight secondary ion mass spectrometry (ToF-SIMS), Cr K-edge X-ray absorption near edge structure (XANES)/extended X-ray absorption fine structure (EXAFS), and electron paramagnetic resonance (EPR). Adsorption isotherms and kinetics were successfully fit to Langmuir and pseudo-second-order kinetic models, respectively, consistent with monotonic uptake of Cr(OH)4- monomers until saturation coverage of approximately half the aluminum surface site density. High resolution AFM revealed monolayer cluster self-assembly on the (010) basal surfaces with increasing Cr(III) loading, possessing a structural motif similar to guyanaite (β-CrOOH), stabilized by corner-sharing Cr-O-Cr bonds and attached to the surface with edge-sharing Cr-O-Al bonds. The selective uptake appears related to short-range surface templating effects, with bridging metal connections likely enabled by hydroxyl anion ligand exchange reactions at the surface. Such a cluster formation mechanism, which stops short of more laterally extensive heteroepitaxy, could be a metal uptake discrimination mechanism more prevalent than currently recognized.

Phase Formation in Phosphate and Borophosphate Glasses Containing Iron, Chromium, Nickel, and Sulfur

We have prepared multicomponent phosphate and borophosphate glass systems containing considerable concentrations of high-level waste components critical to the vitrification process, such as iron, chromium, nickel, and sulfur, which imitate the composition of the high-level waste in storage tanks. We have studied the glass preparation temperature, viscosity, phase formation, thermal stability, and hydrolytic stability of the materials. The lowest rate of cesium leaching from quenched boron-free aluminophosphate glasses was on the order of 10–5 g/(cm2 day).

A multiple lines of evidence approach for identifying geologic heterogeneities in conceptual site models for performance assessments.

Model-based decision making is commonly used in performance assessments to assure water resource protection for both human health and the environment for hundreds of years into the future. To make decisions regarding aquifer protection against potential contamination, a conceptual site model (CSM) describing the hydrodynamic behavior needs to account for subsurface heterogeneities in sufficient detail. When site-specific data are sparse, larger-scale geologic descriptions are adopted with the consequence of losing small-scale features (at the cm scale) that can control contaminant transport. In this study, a multiple lines of evidence approach is used to construct vadose zone CSMs based on an evaluation of several types of data, including geologic logs, borehole moisture content and concentration data, geophysical spectral gamma logging data, and groundwater concentration data for a tank farm at the Hanford Site in southeastern Washington State. The resulting CSMs of the unsaturated zone represent a synthesis of what is known about flow and transport processes at the site-scale and maintain consistency with knowledge that has been accumulated at the regional scale. Through a process of extensive data analyses, a systematic approach is described to create an evidence base that supports the evaluation and development of CSMs. Numerical models are then used to evaluate the impact that smaller-scale heterogeneities have on contaminant transport through the vadose zone for a performance assessment on waste tank closure. Together, the field data and the numerical experiments suggest that although small-scale features close to source releases can have an impact on horizontal spreading, overall there is a relatively minor impact on transport for the site under study as evaluated by differences in peak fluxes and arrival times for historical leak events, and for potential releases resulting from waste tank closure. Use of alternative CSMs, developed through careful examination of available characterization and monitoring data, provides confidence that geologic heterogeneities do not impact contaminant transport behavior significantly enough to alter the assessment of risk for closure at this site.